Treatment of epoxidized unsaturated isoolefin copolymers

ABSTRACT

A process for producing a crosslinked polymer involves contacting an epoxidized unsaturated isoolefin copolymer with a catalytic amount of an acid in an absence of a solvent. A process for producing a hydroxylated unsaturated isoolefin copolymer involves contacting an epoxidized unsaturated isoolefin copolymer with a catalytic amount of an acid in an absence of a solvent. A hydroxylated unsaturated isoolefin copolymer having hydroxyl groups in endo configurations may be produced thereby.

FIELD

This application relates to polymers, in particular to processes fortreating epoxidized unsaturated isoolefin copolymers and productsproduced therefrom.

BACKGROUND

Poly(isobutylene-co-isoprene), or IIR, is a synthetic elastomer commonlyknown as butyl rubber which has been prepared since the 1940's throughthe random cationic copolymerization of isobutylene with small amountsof isoprene (1-5 mole %). As a result of its molecular structure, IIRpossesses superior air impermeability, a high loss modulus, oxidativestability and extended fatigue resistance.

Butyl rubber is understood to be a copolymer of an isoolefin and one ormore, preferably conjugated, multiolefins as comonomers. Commercialbutyl comprises a major portion of isoolefin and a minor amount, usuallynot more than 2.5 mol %, of a conjugated multiolefin. Butyl rubber orcopolymer is generally prepared in a slurry process using methylchloride as a diluent and a Friedel-Crafts catalyst as part of thepolymerization initiator. This process is further described in U.S. Pat.No. 2,356,128 and Ullmanns Encyclopedia of Industrial Chemistry, volumeA 23, 1993, pages 288-295, the entire contents of which are hereinincorporated by reference.

Functionalization of polyisobutylene-co-isoprene (butyl rubber) is ofgreat interest due to its potential applications in technology areassuch as surface modification, adhesion, drug delivery, compatibilizationof polymer blends, and motor oil and fuel additives, and in providingclean cured products without contaminant leaching and/or side products.Recent advancement in the functionalization of butyl rubber has gainedconsiderable interest especially in the field of grafting ofpoly(ethylene oxide) (PEO) onto epoxidized butyl polymer due to thepotential application in biomedical applications as well as the enhancedmechanical properties, increased wettability, microphase separation, andemulsifying properties observed in these polymers.

Typically, reactions involving epoxidized butyl polymer have beenperformed in solution. For example, US 2013/345367 published Dec. 26,2013 describes a reaction where epoxidized butyl rubber was reacted witha catalytic amount of concentrated aqueous HCl in toluene at roomtemperature to afford a ring-opened product.

Still, there remains a need for improved processes involving epoxidizedbutyl rubber to produce products.

SUMMARY

There is provided a process for producing a crosslinked polymer,comprising contacting an epoxidized unsaturated isoolefin copolymer witha catalytic amount of an acid in an absence of a solvent.

There is provided a process for producing a hydroxylated unsaturatedisoolefin copolymer, comprising contacting an epoxidized unsaturatedisoolefin copolymer with a catalytic amount of an acid in an absence ofa solvent.

There is provided a hydroxylated unsaturated isoolefin copolymercomprising hydroxyl groups in endo configurations.

Further features will be described or will become apparent in the courseof the following detailed description. It should be understood that eachfeature described herein may be utilized in any combination with any oneor more of the other described features, and that each feature does notnecessarily rely on the presence of another feature except where evidentto one of skill in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

For clearer understanding, preferred embodiments will now be describedin detail by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 depicts a reaction scheme for crosslinking of epoxidized butylrubber catalyzed by a strong acid in an absence of solvent to produce acrosslinked network of butyl rubber polymers.

FIG. 2 depicts MDR plots (torque (dNm) vs. time (min)) at 1 arc atdifferent temperatures (25° C., 30° C., 40° C., 100° C.) for a compoundcomprising 100 phr epoxidized butyl rubber (ERB301) and 0.5 phrp-toluenesulfonic acid (PISA).

FIG. 3 depicts MDR plots (torque (dNm) vs. time (min)) at 1 arc at 180°C. for purified solution epoxidized butyl rubber cured with the additionof mCBA (trace with dark squares), and solid state epoxidized butylrubber cured with mCBA formed in situ during the production of theepoxidized butyl rubber (trace with no squares).

FIG. 4 depicts a graph of strain (%) vs. time (min) illustrating creepprofiles for epoxidized butyl rubber before and after ultraviolet (UV)curing at 25° C.

DETAILED DESCRIPTION

In accordance with the present invention, a process for producing ahydroxylated unsaturated isoolefin copolymer comprises contacting anepoxidized unsaturated isoolefin copolymer with a catalytic amount of anacid in an absence of a solvent. The epoxidized unsaturated isoolefincopolymer may be contacted with the acid by mixing the two together toform a polymer compound, for example in a mixer, and allowing the acidto catalyze ring-opening of epoxide functional groups to producehydroxyl groups on the unsaturated isoolefin copolymer. Further reactionunder the same conditions can then produce a crosslinked polymer. Theepoxidized unsaturated polymer may be in a solid state, but typicallyhas sufficient processibility in a mixer to permit mixing with the acid.Suitable mixers include, for example, paddle mixers, sonic agitators,mills (e.g. ball mills, roll mills), Banbury™ mixers, Brabender™ mixers,extruders (e.g. single screw, twin screw), rotary mixers and the like.

In one embodiment, the epoxidized unsaturated isoolefin copolymer may beutilized in situ in a compound produced during the production of theepoxidized unsaturated isoolefin copolymer. When the epoxidizedunsaturated isoolefin copolymer is utilized in situ, acid may be addedto and mixed in the epoxidized unsaturated isoolefin copolymer todisperse the acid therein to form a polymer compound comprising theepoxidized unsaturated polymer and the acid. In another embodiment, theacid may be produced as a side product in the production of theepoxidized unsaturated isoolefin copolymer to directly form a polymercompound comprising the epoxidized unsaturated isoolefin copolymer andthe acid.

Prior art processes to form hydroxylated unsaturated isoolefincopolymers produce allylic alcohol functionalized unsaturated polymerswhere the hydroxyl groups are in exo configurations. In the presentprocess, the polymer compound may comprise unsaturated isoolefincopolymers with hydroxyl groups in exo configurations (allylic alcohol),unsaturated isoolefin copolymers with hydroxyl groups in endoconfigurations, unsaturated isoolefin copolymers with hydroxyl groups inboth exo and endo configurations, or mixtures thereof.

Conversion of epoxide functional groups on the epoxidized unsaturatedisoolefin copolymer to hydroxyl functional groups in the presence of acatalytic amount of the acid may be accomplished at ambient temperature(e.g. room temperature) or greater. The type of product formed may becontrolled by a balance between temperature and acid strength. The useof stronger acids at relatively lower temperatures leads to ring openingand the formation of hydroxylated unsaturated isoolefin copolymers, butfurther leads to self-crosslinking and the formation of a cross-linkednetwork of isoolefin copolymers. Effectively, the stronger acid curesthe epoxidized unsaturated isoolefin copolymers, the curing beingaccomplished at lower temperatures than hitherto possible for butylrubber or functionalized butyl rubber. The use of weaker strength acidsleads to epoxide ring opening and the production of hydroxylatedunsaturated isoolefin copolymers, which may be isolated cleanly withlittle or no crosslinked product with appropriate temperature and timecontrol. Weaker acids may also lead to crosslinking at highertemperatures.

The temperature at which the acid is contacted with epoxidizedunsaturated isoolefin copolymer is preferably in a range of from ambienttemperature to about 250° C. If the acid has a pKa less than or equal toabout 3, the epoxidized unsaturated isoolefin copolymer may becrosslinked at temperatures less than or equal to about 250° C. If theacid has a pKa less than or equal to about 1, the epoxidized unsaturatedisoolefin copolymer may be crosslinked at temperatures as low as roomtemperature. The temperature used to crosslink the epoxidizedunsaturated isoolefin copolymer may be guided by applicationrequirements.

When a crosslinked network is the desired product and a stronger acid isused, the temperature is desirably about 20° C. or greater and about100° C. or lower. More preferably the temperature is about 25° C. orgreater. More preferably the temperature is about 75° C. or lower, evenmore preferably about 60° C. or lower.

When a crosslinked network is the desired product and a weaker acid isused, the temperature is desirably about 160° C. or greater. Preferably,the temperature is about 250° C. or lower. More preferably thetemperature is about 160° C. or greater and about 200° C. or lower.

When a hydroxylated unsaturated isoolefin copolymer is the desiredproduct and a weaker acid is used, the temperature is desirably about180° C. or lower, or about 160° C. or lower. Preferably, the temperatureis about 60° C. or higher, or about 100° C. or higher, or about 140° C.or higher.

Production of the product is relatively fast. Production of the productmay occur within about 2 hours or less, or even about 1 hour or less, oreven about 30 minutes or less, or even about 10 minutes or less or evenabout 5 minutes or less. Production time depends to some extent ontemperature; therefore reactions performed at higher temperature maytake less time. The time for reactions intended to produce hydroxylatedunsaturated isoolefin copolymers is especially influenced by thetemperature.

The acid is used in a catalytic amount. A catalytic amount is preferablyin a range of about 0.01-10 phr (part per hundred of rubber), morepreferably in a range of 0.1-7 phr. Stronger acids are acids having apKa of about 1 or lower. Weaker acids have a pKa of greater thanabout 1. Some examples of stronger acids include sulfonic acids, forexample p-toluenesulfonic acid (PTSA, pKa −2.80), methanesulfonic acid(pKa −2.0) and mixtures thereof. Some examples of weaker acids includesalicylic acid (pKa 2.97), benzoic acid (pKa 4.2), an analogue ofbenzoic acid, acetic acid and mixtures thereof. Preferred weaker acidsinclude benzoic acid, an analogue of benzoic acid or a C₁-C₇ alkanoicacid. Preferred weaker acids comprise a compound of formula (I) or (II):

where R₁, R₂, R₃, R₄ and R₅ are independently hydrogen, methyl, ethyl,phenyl, chloro or bromo, and R₆ is hydrogen, methyl, ethyl, propyl,butyl, pentyl or hexyl. Preferably, one of R₁, R₂, R₃, R₄ and R₅ ischloro. Preferably four of R₁, R₂, R₃, R₄ and R₅ are hydrogen. Thebenzoic acid or analogue of benzoic acid preferably comprisesmeta-chlorobenzoic acid (mCBA, pKa 3.81). The C₁-C₇ alkanoic acidpreferably comprises acetic acid.

Epoxidized Unsaturated Isoolefin Copolymer.

The epoxidized unsaturated isoolefin copolymer may be produced by atleast partial epoxidation of an unsaturated isoolefin copolymer by anysuitable method. A variety of methods for epoxidizing unsaturatedisoolefin copolymer are known in the art. For example, it is known thatthe unsaturated isoolefin copolymer may be treated with a hydrogenperoxide precursor, often with the aid of a catalyst, to epoxidizeethylenic bonds in the unsaturated isoolefin copolymer. Catalysts mayinclude, for example, transition metal complexes such asZiegler/Natta-type catalysts (e.g. neodymium-based), molybdenumcomplexes (e.g. molybdenum naphthenate), vanadium complexes (e.g.acetylacetone vanadium complex) titanium complexes, tungsten compounds(e.g. tungsten oxide) and mixtures thereof.

The treatment may be performed in a solvent or in an absence of asolvent. Whether the treatment is in a solvent or in an absence of asolvent, a suitable mixer may be utilized during the treatment todisperse the hydrogen peroxide precursor in the unsaturated isoolefincopolymer. Producing the epoxidized unsaturated isoolefin copolymer in asolid state reaction in an absence of a solvent is preferred. Theunsaturated polymer may be in a solid state, but typically hassufficient plasticity to permit mixing with the hydrogen peroxideprecursor. Suitable mixers include, for example, paddle mixers, sonicagitators, mills (e.g. ball mills, roll mills), Banbury™ mixers,Brabender™ mixers, extruders (e.g. single screw, twin screw), rotarymixers and the like. Once produced, the epoxidized unsaturated isoolefincopolymer may be first isolated, and possibly purified, beforecontacting with acid, or may be contacted in situ with acid to form theproduct.

Hydrogen peroxide precursors suitable for epoxidizing the unsaturatedisoolefin copolymer include, but are not limited to, hydrogen peroxide,inorganic peroxides, organic peroxides and mixtures thereof. Organicperoxides or mixtures thereof are preferred. Some organic peroxidesinclude, for example, alkyl peroxides, alkyl hydroperoxides (e.g.tert-butyl hydroperoxide, ethyl hydroperoxide), peroxy acids andmixtures thereof. Peroxy acids or mixtures thereof are preferred. Peroxyacids or mixtures thereof are preferred. Some peroxy acids include, forexample, peroxybenzoic acid, analogues of peroxybenzoic acid,peroxyacetic acid, peroxybenzoic acid, trifluoroperoxyacetic acid,magnesium mono-peroxyphthalate or mixtures thereof. Organic peroxy acidswhich are compounds of formula (III) or (IV) are preferred:

where R₁, R₂, R₃, R₄ and R₅ are independently hydrogen, methyl, ethyl,phenyl, chloro or bromo, and R₆ is hydrogen, methyl, ethyl, propyl,butyl, pentyl or hexyl. Preferably, one of R₁, R₂, R₃, R₄ and R₅ ischloro. Preferably four of R₁, R₂, R₃, R₄ and R₅ are hydrogen. Theperoxy acid preferably comprises meta-chloroperoxybenzoic acid (mCPBA)or peracetic acid. Of particular note are peroxy acids of formula (III)or (IV) because the use of such peroxy acids to epoxidize theunsaturated polymer results in the production of acids of formula (I) or(II) as side products, and the presence of acids of formula (I) or (II)already well-dispersed in the epoxidized unsaturated polymer compoundsremoves the need to add and mix the acid to effect epoxide ring-opening.

In using a peroxy acid to epoxidize the unsaturated isoolefin copolymer,the unsaturated isoolefin copolymer is preferably mixed with the peroxyacid at a temperature at or above ambient temperature. Ambienttemperature is the temperature at which the unsaturated isoolefincopolymer is being mixed with the peroxy acid in an absence ofexternally applied heating. The mixing process itself provides heat,which aids in the mixing process by softening the polymer. To reduce thechance of polymer degradation, it is preferable to mix the unsaturatedisoolefin copolymer with the peroxy acid at a temperature of no morethan about 95° C., more preferably no more than about 75° C., morepreferably no more than about 65° C. and more preferably no more thanabout 50° C. While the act of mixing may raise the ambient temperatureto about 30° C. or even higher, in some embodiments it may be desirableto apply more heat to raise the temperature even higher. In someembodiments, the unsaturated isoolefin copolymer may be mixed with theperoxy acid at a temperature in a range of ambient temperature to about95° C., in a range of ambient temperature to about 75° C., or in a rangeof ambient temperature to about 50° C. In some embodiments, unsaturatedisoolefin copolymer may be mixed with the peroxy acid at a temperaturein a range of about 20° C. to about 95° C., or in a range of about 30°C. to about 50° C. In one preferred embodiment, the temperature at whichthe unsaturated isoolefin copolymer is mixed with the peroxy acid isambient temperature in an absence of externally applied heating.

The unsaturated isoolefin copolymer is preferably mixed with the peroxyacid for a length of time less than about 4 hours, more preferably lessthan about 1 hour, yet more preferably less than about 0.5 hour. In oneembodiment, the length of time may be about 10 minutes or less. Inanother embodiment, the length of time may be about 5 minutes or less.In some embodiment, the length of time may be 30 seconds or more, or 1minute or more, or 2 minutes or more.

The peroxy acid is preferably mixed with the unsaturated polymer in anabsence of solvent. The unsaturated polymer is in a solid state;however, the unsaturated polymer typically has sufficient processibilityin a mixer to permit mixing with the peroxy acid. The peroxy acid may bea solid or a liquid. Peroxy acid in the solid state is preferred. Mixingof solid unsaturated isoolefin copolymer and peroxy acid may beaccomplished using any suitable mixer in the art. Some examples ofmixers for polymers and polymer additives include mills (e.g. rollmills, ball mills), blade mixers, internal mixers (e.g. Banbury™ andBrabender™ mixers), extruders (twin screw, single screw) and the like.Mills are particularly preferred. With a view to effective mixercapacity and the amount of unsaturated isoolefin copolymer and peroxyacid used, the time, temperature and shear while mixing may becontrolled to optimize conversion efficiency.

The peroxy acid may be used in an amount considerably less than in othersolid state epoxidation processes in the art. The peroxy acid ispreferably used in an amount of about 5 mol % or less equivalents tounsaturation, even about 3 mol % or less equivalents to unsaturation,while having high conversion efficiency of the unsaturated isoolefincopolymer to the epoxidized polymer. In some embodiments, suitableamounts of the peroxy acid are in a range of 0.1-5 mol %, or 0.4-4 mol %or 0.7-3 mol % equivalents to unsaturation.

For enhanced control over fast kinetics of the epoxidation reaction, amasterbatch approach to mixing is preferred. In this approach, theperoxy acid may be supported on a support matrix, for example a matrixcomprising a saturated polymer, and the supported peroxy acid mixed withunsaturated isoolefin copolymer. The saturated polymer preferablycomprises a saturated elastomer. Some examples of saturated polymersinclude polyisobutylene (IB), epichlorohydrin rubber (ECO), polyacrylicrubber (ACM, ABR), silicone rubber (SI, Q, VMQ), fluorosilicone rubber(FVMQ), fluoroelastomers (FKM, and FEPM), perfluoroelastomers (FFKM),polyether block amides (PEBA), chlorosulfonated polyethylene (CSM),ethylene-vinyl acetate (EVA) or mixtures thereof. The saturated polymerpreferably comprises a polyisobutylene. Low or medium molecular weightpolyisobutylenes are preferred.

Using a peroxy acid as described above to epoxidize the unsaturatedisoolefin copolymer may have one or more advantages including requiringno solvent, requiring no catalyst, requiring no or little appliedexternal heat input, requiring no applied cooling, requiring lessepoxidation agent, being faster, and/or resulting in more efficientconversion of the polymer.

The unsaturated isoolefin copolymer preferably comprises repeating unitsderived from at least one isoolefin monomer and repeating units derivedfrom at least one multiolefin monomer.

The isoolefin copolymer is not limited to a special isoolefin. However,isoolefins within the range of from 4 to 16 carbon atoms, preferably 4-7carbon atoms, such as isobutene, 2-methyl-1-butene, 3-methyl-1-butene,2-methyl-2-butene, 4-methyl-1-pentene and mixtures thereof arepreferred. More preferred is isobutene (isobutylene).

The isoolefin copolymer is not limited to a special multiolefin. Everymultiolefin copolymerizable with the isoolefin known by the skilled inthe art can be used. However, multiolefins within the range of from 4-14carbon atoms, such as isoprene, butadiene, 2-methylbutadiene,2,4-dimethylbutadiene, piperyline, 3-methyl-1,3-pentadiene,2,4-hexadiene, 2-neopentylbutadiene, 2-methly-1,5-hexadiene,2,5-dimethly-2,4-hexadiene, 2-methyl-1,4-pentadiene,2-methyl-1,6-heptadiene, cyclopentadiene, methylcyclopentadiene,cyclohexadiene, 1-vinyl-cyclohexadiene and mixtures thereof, preferablyconjugated diener, are used. Isoprene is more preferably used. Theunsaturated polymer useful in the present invention may include aco-monomer other than the above referenced multiolefins, such as analkyl-substituted vinyl aromatic co-monomer, including but not limitedto a C₁-C₄ alkyl substituted styrene, for example para-methylstyrene.

As optional monomers, any monomer copolymerizable with the isoolefinsand/or dienes known by the skilled in the art can be used. α-methylstyrene, p-methyl styrene, chlorostyrene, cyclopentadiene andmethylcyclopentadiene are preferably used. Indene and other styrenederivatives may also be used. The unsaturated polymer can include, forexample, random copolymers of isobutylene, isoprene and para-methylstyrene.

In one embodiment, the isoolefin copolymer may be formed bycopolymerization of a monomer mixture. Preferably, the monomer mixturecomprises about 80-99.9 mol % of at least one isoolefin monomer andabout 0.1-20 mol % of at least one multiolefin monomer, based on themonomers in the monomer mixture. More preferably, the monomer mixturecomprises about 90-99.9 mol % of at least one isoolefin monomer andabout 0.1-10 mol % of at least one multiolefin monomer. In oneembodiment, the monomer mixture comprises about 92.5-97.5 mol % of atleast one isoolefin monomer and about 2.5-7.5 mol % of at least onemultiolefin monomer. In another embodiment, the monomer mixturecomprises about 97.4-95 mol % of at least one isoolefin monomer andabout 2.6-5 mol % of at least one multiolefin monomer.

If the monomer mixture comprises the optional monomer copolymerizablewith the isoolefins and/or dienes, the optional monomer preferablyreplaces a portion of the multiolefin monomer. The monomer mixture mayalso comprise from 0.01% to 1% by weight of at least one multiolefincross-linking agent, and when the multiolefin cross-linking agent ispresent, the amount of multiolefin monomer is reduced correspondingly.

The isoolefin copolymer may be formed by copolymerization of a monomermixture, for example by solution polymerization. A solutionpolymerization reaction is performed in the presence of an initiatorsystem (e.g. a Lewis acid catalyst and a proton source) capable ofinitiating the polymerization process. A proton source suitable in thepresent invention includes any compound that will produce a proton whenadded to the Lewis acid or a composition containing the Lewis acid.Protons may be generated from the reaction of the Lewis acid with protonsources to produce the proton and the corresponding by-product. Suchreaction may be preferred in the event that the reaction of the protonsource is faster with the protonated additive as compared with itsreaction with the monomers. Proton generating reactants include, forexample such as water, alcohols, phenol thiols, carboxylic acids, andthe like or any mixture thereof. Water, alcohol, phenol or any mixturethereof is preferred. The most preferred proton source is water. Apreferred ratio of Lewis acid to proton source is from 5:1 to 100:1 byweight, or from 5:1 to 50:1 by weight. The initiator system includingthe catalyst and proton source is preferably present in the reactionmixture in an amount of 0.02-0.1 wt %, based on total weight of thereaction mixture.

Alkyl aluminum halide catalysts are a particularly preferred class ofLewis acids for catalyzing solution polymerization reactions inaccordance with the present invention. Examples of alkyl aluminum halidecatalysts include methyl aluminum dibromide, methyl aluminum dichloride,ethyl aluminum dibromide, ethyl aluminum dichloride, butyl aluminumdibromide, butyl aluminum dichloride, dimethyl aluminum bromide,dimethyl aluminum chloride, diethyl aluminum bromide, diethyl aluminumchloride, dibutyl aluminum bromide, dibutyl aluminum chloride, methylaluminum sesquibromide, methyl aluminum sesquichloride, ethyl aluminumsesquibromide, ethyl aluminum sesquichloride and any mixture thereof.Preferred are diethyl aluminum chloride (Et₂AlCl or DEAC), ethylaluminum sesquichloride (Et_(1.5)AlCl_(1.5) or EASC), ethyl aluminumdichloride (EtAlCl₂ or EADC), diethyl aluminum bromide (Et₂AlBr orDEAB), ethyl aluminum sesquibromide (Et_(1.5)AlBr_(1.5) or EASB) andethyl aluminum dibromide (EtAlBr₂ or EADB) and any mixture thereof. In aparticularly preferred initiator system, the catalyst comprises ethylaluminum sesquichloride, preferably generated by mixing equimolaramounts of diethyl aluminum chloride and ethyl aluminum dichloride,preferably in a diluent. The diluent is preferably the same one used toperform the copolymerization reaction.

One or more other catalysts useful in solution copolymerization ofisoolefins may also be present in the initiator system, for exampletitanium tetrachloride, stannous tetrachloride, boron trifluoride, borontrichloride, or methylalumoxane. The monomers are generally polymerizedcationically, preferably at temperatures in the range of from about−100° C. to about −50° C., preferably in the range of from about −95° C.to about −65° C. The temperature is preferably about −80° C. or greater.

The solution comprises 0-30 vol % of an aliphatic hydrocarbon diluent,based on volume of the solution. In preferred embodiments, the solutioncomprises 0.1-30 vol % or 0.1-20 vol % of the aliphatic hydrocarbondiluent. The aliphatic hydrocarbon may be in a common aliphatic mediumcomprising at least 80 wt % of one or more aliphatic hydrocarbons havinga boiling point in the range of 45° C. to 80° C. at a pressure of 1013hPa, preferably at least 90 wt %, and even more preferably at least 95wt %. Aliphatic hydrocarbons having a boiling point in the range of 45°C. to 80° C. at a pressure of 1013 hPa include cyclopentane,2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane,3-methylpentane, n-hexane, methylcyclopentane and 2,2-dimethylpentane.

A C6 solvent is a particularly preferred choice for use in a solutionprocess. A lower molecular weight solvent, such as C5 or lighter, has aboiling point close to the monomers and the monomers therefore may notbe separable from the solution by distillation. A higher molecularweight solvent, such as C7 or heavier, would be more difficult toseparate from the rubber after halogenation. The solution viscosityprovided by use of a C7 solvent is also significantly higher than with aC6 solvent, making the solution more difficult to handle and impedingheat transfer in the reactor, even when provided with the high monomerto solvent ratios described above. As a result, the C6 solvents of thepresent invention are a preferred selection from among the availablesolvents. C6 solvents suitable for use in the present inventionpreferably have a boiling point of between 50° C. and 69° C. Examples ofpreferred C6 solvents include n-hexane or hexane isomers, such as2-methyl pentane or 3-methyl pentane, or mixtures of n-hexane and suchisomers as well as cyclohexane. The common aliphatic medium may, forexample, further comprise other compounds which are inert underpolymerization conditions such as other aliphatic hydrocarbons, forexample heptanes and octanes having a boiling point of more than 80° C.at a pressure of 1013 hPa, propanes, butanes, n-pentane, cyclohexane aswell as halohydrocarbons such as methylchloride, hydrofluorocarbon (HFC)and other halogenated aliphatic hydrocarbons which are inert underreaction conditions.

Copolymerization process may be performed as a batch process in a batchreactor or a continuous process (e.g. a plug flow process) in acontinuous reactor. In a continuous process, the process is preferablyperformed with at least the following feed streams:solvent/diluent+isoolefin (preferably isobutene)+multiolefin (preferablydiene, isoprene); initiator system; and, optionally, a multiolefincross-linking agent.

It should be noted that the multiolefin crosslinking agent can also beadded in the same feed stream as the isoolefin and multiolefin. Whilecross-linking agents are not necessary to increase molecular weight ofthe copolymer to a processable level, cross-linking agents maynevertheless be used if desired.

To form a halogenated isoolefin copolymer, the isoolefin copolymer maybe subjected to a halogenation process. Bromination or chlorination canbe performed according to a process known by those skilled in the art,for example, the procedures described in Rubber Technology, 3rd Ed.,Edited by Maurice Morton, Kluwer Academic Publishers, pp. 297-300 andfurther documents cited therein. Preferably, halogenation is performedaccording to a process as described in U.S. Pat. No. 5,886,106 issuedMar. 23, 1999, the contents of which is herein incorporated byreference. The amount of halogenating agent added is controlled toprovide a final halogen content of 0.05-2.5 mol % in the halogenatedcopolymer. Halogenation agents useful for halogenating isoolefincopolymer may comprise elemental chlorine (Cl₂) or bromine (Br₂) and/ororgano-halide precursors thereto, for example dibromo-dimethylhydantoin, tri-chloroisocyanuric acid (TCIA), n-bromosuccinimide, or thelike. Preferably, the halogenation agent comprises or is bromine.Preferably, halogenation comprises bromination.

During halogenation of an isoolefin copolymer containing conjugateddienes, such as isoprene, some or all of the multiolefin content of theisoolefin copolymer is converted to allylic halides. The total allylichalide content of the halogenated isoolefin copolymer may not exceed thestarting multiolefin content of the parent isoolefin copolymer. Theallylic halide sites allow for reacting with and attaching a nucleophileto the halogenated isoolefin copolymer. For halogenated isoolefincopolymers containing no allylic halides, for example, halogenatedisoolefin copolymer derived from isobutylene and styrenic monomers,benzylic halides, formed by halogenation of the styrenic monomer, may bereacted to form the ionomer rather than allylic halides. The same logicwould therefore apply to benzylic halides as allylic halides; the totalamount of ionomeric moieties cannot exceed the available amount ofbenzylic halides.

Curing:

If the acid cure system described above is not desired or an additionalcure system is desired, the hydroxylated unsaturated polymer produced bythe process may further be cured by any other suitable method, forexample sulfur-based curatives, peroxide-based curatives, ZnO curatives,resin cure systems or UV light. A typical sulfur-based curing systemcomprises: (i) a metal oxide, (ii) elemental sulfur and (iii) at leastone sulfur-based accelerator. The use of metal oxides as a component inthe curing system is well known in the art. A suitable metal oxide iszinc oxide, which is typically used in the amount of from about 1 toabout 10, preferably from about 2 to about 5, parts by weight perhundred parts by weight polymer in the composition. Elemental sulfur,comprising component (ii) of the preferred curing system is typicallyused in amounts of from about 0.2 to about 10 parts by weight perhundred parts by weight polymer in the composition. Suitablesulfur-based accelerators (component (iii) of the preferred curingsystem) are typically used in amounts of from about 0.5 to about 3 partsby weight, per hundred parts by weight polymer in the composition.Non-limiting examples of useful sulfur-based accelerators may beselected from the thiuram sulfides such as tetramethyl thiuram disulfide(TMTD), the thiocarbamates such as zinc dimethyl dithiocarbamate (ZDC)and the thiazyl and benzothiazyl compounds such as mercaptobenzothiazyldisulfide (MBTS). Preferably, the sulphur based accelerator ismercaptobenzothiazyl disulfide. In some embodiments of a resin curesystem, the resin cure system may comprise a halogenated phenolformaldehyde resin or a phenol formaldehyde resin, optionally inconjunction with an activator. Halogenated phenol formaldehyde resinsand phenol formaldehyde resins are known in the art as described in U.S.Pat. Nos. 2,701,895, 3,093,613 and 3,165,496, which are hereinincorporated by reference. An alkyl phenol-formaldehyde derivative, forexample octylphenol-formaldehyde with methylol active group, is typical.Metal oxides, for example zinc oxide, and/or other curing or processingaids (e.g. stearic acid) may also be used in the resin cure system.Metal oxides may be used in the amount of from about 1 to about 10 partsby weight per hundred parts by weight polymer in the composition. Resinmay be used in amounts of from about 0.2 to about 20 phr. Other curingor processing aids may be used in amounts of from about 0.2 to about 10phr.

UV cured samples of epoxidized or hydroxylated unsaturated isoolefincopolymer demonstrate creep characteristics at 25° C. over about 2 hoursthat is at least about 10 times less than for uncured samples, or evenat least about 15 times less, or even at least about 20 times less, oreven at least about 25 times less.

Additives:

The epoxidized or hydroxylated unsaturated isoolefin copolymer may becompounded with various auxiliary products, shaped into an article, andthe resulting compound cured. Auxiliary products for polymers (e.g.rubbers) include, for example, reaction accelerators, vulcanizingaccelerators, vulcanizing acceleration auxiliaries, antioxidants,foaming agents, anti-aging agents, heat stabilizers, light stabilizers,ozone stabilizers, processing aids, plasticizers, tackifiers, blowingagents, dyestuffs, pigments, waxes, extenders, organic acids,inhibitors, metal oxides, and activators such as triethanolamine,polyethylene glycol, hexanetriol, etc., which are known to the rubberindustry. The rubber aids are used in conventional amounts that depend,inter alia, on the intended use. Further information on vulcanizationmay be obtained in Encyclopedia of Polymer Science and Engineering, Vol.17, s. 666 et seq. (Vulcanization).

In a particular embodiment, the epoxidized or hydroxylated unsaturatedisoolefin copolymer may be compounded with a suitable filler (e.g.mineral and/or non-mineral fillers) to enhance certain desirablephysical properties, such as tensile strength, viscosity, hardness,permeability, etc. Suitable fillers are selected from those that do notimpart undesirable residues or otherwise adversely affect the polymerfor use in the aforementioned “clean” applications. Examples of suitablefillers include silica, silicates, high aspect ratio or nano-sizedversions thereof, and other suitable clean fillers. The selection offiller for imparting desired physical properties while retaining cleancharacteristics is within the purview of persons skilled in the art.Conventional amounts of fillers are from about 1 to 150 phr (parts perhundred rubber).

Uses:

The polymer products produced in accordance with the present process isuseful in various products including inner liners, bladders, tubes, aircushions, pneumatic springs, air bellows, accumulator bags, hoses,conveyor belts and pharmaceutical closures, automobile suspensionbumpers, auto exhaust hangers, body mounts, shoe soles, tire sidewallsand tread compounds, belts, hoses, shoe soles, gaskets, o-rings,wires/cables, membranes, rollers, bladders (e.g. curing bladders), innerliners of tires, tire treads, shock absorbers, machinery mountings,balloons, balls, golf balls, protective clothing, medical tubing,storage tank linings, electrical insulation, bearings, pharmaceuticalstoppers, adhesives, a container, such as a bottle, tote, storage tank,a container closure or lid; a seal or sealant, such as a gasket orcaulking; a material handling apparatus, such as an auger or conveyorbelt; a cooling tower; a metal working apparatus, or any apparatus incontact with metal working fluids; an engine component, such as fuellines, fuel filters, fuel storage tanks, gaskets, seals, etc.; amembrane, for fluid filtration or tank sealing, appliances, babyproducts, bathroom fixtures, bathroom safety, flooring, food storage,garden, kitchen fixtures, kitchen products, office products, petproducts, sealants and grouts, spas, water filtration and storage,equipment, food preparation surfaces and equipment, shopping carts,surface applications, storage containers, footwear, protective wear,sporting gear, carts, dental equipment, door knobs, clothing,telephones, toys, catheterized fluids in hospitals, surfaces of vesselsand pipes, coatings, food processing, biomedical devices, filters,additives, computers, ship hulls, shower walls, tubing, pacemakers,implants, wound dressing, medical textiles, ice machines, water coolers,fruit juice dispensers, soft drink machines, piping, storage vessels,metering systems, valves, fittings, attachments, filter housings,linings, and barrier coatings.

The polymer products are particularly useful in pharmaceuticalapplications (clean cure), microelectronic (transparent material),adhesives, sealants (e.g. window and bathroom caulking) and coatings.

EAMPLES

FIG. 1 depicts a scheme showing a self-crosslinking reaction whenepoxidized butyl rubber (1) is treated with a catalytic amount of astrong acid in an absence of a solvent at a temperature of about 100° C.or less. The cross-linking reaction may proceed via an epoxidering-opening reaction to form hydroxylated butyl rubber in exo (2)and/or endo (3) configurations. However, further reaction takes placewherein the butyl rubber chains are joined together (i.e. crosslinking)perhaps via an intermolecular dehydration step to form a crosslinkednetwork of butyl rubber chains. In essence, the scheme illustrated inFIG. 1 represents a low temperature cure system for epoxidized butylelastomer.

Using a weaker acid permits ready termination of the reaction at theformation of hydroxylated butyl rubber, which may then be convenientlyand cleanly isolated for use in further applications. However, using aweaker acid at a higher temperature may also lead to the formation of acrosslinked network of butyl rubber chains.

Example 1: Strong Acid Cure System for Epoxidized Butyl Rubber

100 phr epoxidized butyl rubber (ERB301) was dry compounded with 0.5 phrof solid p-toluenesulfonic acid (PTSA) to produce a compound comprisingthe ERB301 and PTSA dispersed therein. Cure profiles of the compoundwere then determined in a moving die rheometer (MDR) using ASTM D5289test procedure at 25° C., 30° C., 40° C. and 100° C. The results areshown in FIG. 2. As seen in FIG. 2, the compound is readily cured attemperatures of about 100° C. or lower, down to about 25° C., within 30minutes, with the majority of the curing occurring within 10 minutes.

Example 2: Weaker Acid Cure System for Epoxidized Butyl Rubber(Epox-IIR)

An epoxidized butyl rubber (ERB301) was prepared from a butyl rubber(RB301) and a mixture of formic acid and hydrogen peroxide in solution.The ERB301 formed in this way was then isolated and purified. Thepurified ERB301 was then dry compounded with 6 phr meta-chlorobenzoicacid (mCBA) for 30 minutes at 140° C. in a Brabender mixer with Banburyrotors to form a hydroxylated butyl rubber (Ex. A). Ex. A comprised0.54% exo-OH, 0.17% endo-OH, 0.74% epoxy and 0.03% conjugated diene(CDB).

Another epoxidized butyl rubber (ERB301) was prepared by dry compounding300 g butyl rubber (RB301) with 18 g of meta-chioroperoxybenzoic acid(mCPBA) on a 6×12 mill for 5 minutes at 50° C. in producing ERB301 inthis manner, meta-chlorobenzoic acid (mCBA) is produced in situ as aside product. The compound was then mixed for 30 minutes at 140° C. in aBrabender mixer with Banbury rotors to form a hydroxylated butyl rubber(Ex. B). Ex. B comprised 0.5% exo-OH, 0.1% endo-OH, 0.5% epoxy and 0.1%CDB.

Cure profiles of Ex. A and Ex. B were then determined in a moving dierheometer (MDR) using ASTM D5289 test procedure at 180° C. The resultsare shown in FIG. 3. As seen in FIG. 3, epoxidized butyl rubber producedby dry compounding butyl rubber with mCPBA to produce in situ mCBA givesa similar cure curve to purified epoxidized butyl rubber that has mCBAadded prior to compounding.

Example 3: UV Curing

Purified epoxidized butyl rubber produced in accordance with Example 2was cured by UV treatment in the presence of a photoacid.

Creep characteristics of the uncured epoxidized butyl rubber and the UVcured epoxidized butyl rubber were measured at 25° C. using an AntonPear MC-301 rheometer in accordance with ASTM F38-00(2014). The resultsare illustrated in FIG. 4. it is evident from FIG. 4 that the UV curedsample exhibits very little creep over the entire 2 hour test time,whereas the uncured sample exhibits a dramatic initial rate of increasein creep which slows down over time but continues to increase.

The novel features will become apparent to those of skill in the artupon examination of the description. It should be understood, however,that the scope of the claims should not be limited by the embodiments,but should be given the broadest interpretation consistent with thewording of the claims and the specification as a whole.

1. A process for producing a crosslinked polymer, the process comprisingcontacting an epoxidized unsaturated isoolefin copolymer with acatalytic amount of an acid in an absence of a solvent.
 2. The processaccording to claim 1, wherein the add has a pKa of about 1 or lower. 3.The process according to claim 2, wherein the contacting is performed ata temperature of about 20° C. to about 100°.
 4. The process according toclaim 2, wherein the acid comprises a sulfonic acid such as for examplep-toluenesulfonic acid.
 5. The process according to claim 1, wherein theacid has a pKa of greater than about
 1. 6. The process according toclaim 5, wherein the contacting is performed at a temperature of about160° C. to about 250° C.
 7. A process for producing a hydroxylatedunsaturated isoolefin copolymer, the process comprising contacting anepoxidized unsaturated isoolefin copolymer with a catalytic amount of anacid in an absence of a solvent.
 8. The process according to claim 7,wherein the add has a pKa of greater than about
 1. 9. The processaccording to claim 8, wherein the contacting is performed at atemperature of about 60° C. to about 180° C.
 10. The process accordingto claim 5, wherein the add comprises a compound of formula (I);

where R₁, R₂, R₃, R₄ and R₅ independently hydrogen, methyl, ethyl,phenyl, chloro or bromo or in one embodiment wherein one of R₁, R₂, R₃,R₄ and R₅ is chloro and four of R₁, R₂, R₃, R₄ and R₅ are hydrogen. 11.The process according to claim 5, wherein the acid comprises a compoundof formula (II):

where R₆ is hydrogen, methyl, ethyl, propyl, butyl, pentyl or hexyl. 12.The process according to claim 5, wherein the acid is produced in situwith production of the epoxidized unsaturated isoolefin copolymer in anabsence of a solvent.
 13. The process according to claim 1, wherein thecatalytic amount is about 0.01-10 phr.
 14. The process according toclaim 1, wherein the isoolefin copolymer comprises repeating unitsderived from at least one isoolefin monomer and repeating units derivedfrom at least one multiolefin monomer.
 15. The process according toclaim 14, wherein the isoolefin monomer comprises isobutane and/orwherein the at least one multiolefin monomer comprises isoprene.
 16. Ahydroxyiated unsaturated isoolefin copolymer comprising hydroxyl groupsin endo configurations,
 17. The copolymer according to claim 16, whereinthe isoolefin copolymer comprises repeating units derived from at leastone isoolefin monomer and repeating units derived from at least onemultiolefin monomer.
 18. The copolymer according to claim 17, whereinthe isoolefin monomer comprises isobutene and/or wherein the at leastone multiolefin monomer comprises isoprene.
 19. The process according toclaim 1, wherein: the catalytic amount is about 0.01-10 phr; if the acidhas a pica of about 1 or lower, the contacting is performed at atemperature of about 25° C. to about 60° C.; and if the acid has a pKaof greater than about 1, the contacting is performed at a temperature ofabout 180° C. to about 200° C.
 20. The process according to claim 1,wherein: wherein the acid comprises a compound of formula (II):

where R₆ is hydrogen, methyl, ethyl, propyl, butyl, pentyl or hexyl; andthe isoolefin copolymer comprises repeating units derived fromisobutane, and repeating units derived from isoprene.